What is washout in the context of wing design?

In the context of wing design, washout refers to a specific aerodynamic feature where the angle of incidence decreases towards the wingtip. This design is intentional and serves multiple purposes. By incorporating washout, the wing is designed to stall more gradually, with the root portion of the wing experiencing a stall before the tip. This ensures that the aircraft retains better control and controllability in a stall scenario, helping the pilot maintain aileron effectiveness and reducing the risk of loss of control due to adverse yaw.

The incorporation of washout can lead to improved handling characteristics, particularly during slow flight and landing phases, where it is vital for the wing to accommodate changes in angle of attack without losing lift abruptly at the wingtip. This helps maintain a degree of aileron effectiveness even as the wing approaches stall conditions.

The other options mentioned do not correctly characterize washout. For example, an increase in angle of incidence at the wingtip, which would imply a more positive angle at the wingtip compared to the root, does not enhance stall recovery or control effectiveness as washout does. Similarly, the reduction of wing surface area or leading-edge curvature do not pertain to washout and affect different aerodynamic properties unrelated to the angle of incidence toward the wingtips